Power plant of the free piston type



July 8, 1947. WELSH 7 2,423,472

POWER PLANT OF THE FREE PISTON TYPE Filed July 24, 1944 5 Sheets-Sheet 1 Inventdr:

obert Jdhl h $4.4, 24...;

Attorney July 8,1941 J, WELSH 2,423,472

' POWER PLANT OF THE FREE PISTON TYPE Filed July 24, 1944 5 Sheets-Sheet 2 FIG 2.

July 8, 1947. E. H 2,423,472

POWER PLANT OF THE FREE PISTON TYPE Filed July 24, 1944 5 Sheets-Sheet :5

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obert Jga'elsl B [MAttorney July 8, 1947. R. J. WELSH POWER PLANT OF THE FREE PISTQN TYPE Filed Jul 24, 1944 5 Sheets-Sheet 4 Int! j Robert J Inventor: .Welsh 'A ttorney Jul 8, 1947.

R. J. WELSH POWER FLANT OF THE FREE PISTON TYPE Filed July 24, 1944 5 Sheets-Shed 5 O, 1 a: 44 h f m O a I 612 I 67 a v I T 34-- T a \fi' 44 v5L? a- 3 a v Fig. -6.

Inverziar.

components acting' forvarying times. .ingly; the components are preferably started; and

Patented July 8, 19 47 POWER PLANT OF THE FREE PISTON Robert James Welsh, Rugby, to The English Electric ,London, England, a British England, or Company limited,

company' Application July 24, 1944, Serial No. 546,359

In Great Britain November 4,1942

r 5 Claims. 1 v

This invention relates tov the operation of a power plant made up of'c'omponents of which the number in 1 operation and their combined output is automatically varied in accordance with the load on the plant. The object of the invention is to providesirnpler means than hitherto known for serving the dual purpose of determining the output of each component and controlling the starting and stoppin thereof while tending to equalise. the length oi time during which individual components are in operation by the same cyclic order.

Thus, assuming that a plant comprises componentsIF-MNPQR, the minimum total load, in one mode of operation, is always supplied by component L; with progressive'lncrease in load the output of'component L i automatically increased until it reachesa certain value, component M is then bro'ught'into operation and its output progressively increased until subsequently component/N- is brought-"into operation, while on decrease of load the procedure is re- 'versed' until component is put out 01' oper- 'ation and component L aloneremains in' oper-' ation. With such a mode of operation component L'may be substantially continuouslyactine, com

' ensuring that the components start and stop in iii accordance with consumer.

ponent R very seldom in operation an'dtheother Accordstopp d in the samecyclid'order; Thus, forex P; and subsequent =increases by starting component L; and soon, while a decrease in load m Fig," il 'fReferring. to this figure, "of the free piston type internalccmh pressor comprises the engine cylind r of compressor cylinders Eat cpposit ample, if the chosen order be Rf'then'when components N" P-'and,Q are in operation an increase of 'loa'dj beyonditheir com- 'bined capacity is 'met by'starti'ng component below a predetermined'value is met by theistopi pingf or putting out or ,action ofco'mponentgN and subsequent decreases by 'the putting out 'of action-of 'con'iponent. Pjand'so on. The object oithe present invention is toachieve the variattlon of power output and the desired starting and stopping in cyclic order by'providing each 1 cqmponent with its own individual control device, 'oi -a -simple kind-;whereby' any desired; power plant can be built up by taking thedesired munber of components each with its individual a controlling" and output-determiningdevice, and appropriately connecting these devices together and to: common means i for determining the total output.

Broadly the invention "consist in providinig each." component with a servo-motor device a 'exhaust ports lb inLthe latter open into adapted (2) to operate the output regulator torts order when the desired output reaches a c certain of the controlling parts shown in i suction inlet id and-at lea s 'tion with 'theconduits can the annular space surrounding the the associated component, (it) to starting signal for the next component i value or values, and (iii) to ensure on redwti oi the desired output below a certain value A a component next in cyclic order either i at rest or to the last one to start iaetonpec One form of complete pcwerplant n ing the invention is shown in. outline l and 2 of the accompanying drawings of Fig. 3 is an enlarged view partlyin see associated with one of the components Fig. i is an enlargedview partly one of the power components and other e ling parts associated therewith.- Fig. i a detail of Figured on larger scale. and 6 illutrate different positions valve. r The power components in this case are combustion compressors operating iuel injection, the compressors supplying sumer, shown as a turbine, in coma number oiccmpremorsin action. hined output being determinede the. load 'rn plantshown mates. four components L--- Mf-ilfem; P, l sxsim lartoL width; as shown in r or and the pair of b'i fie'r cylinders treme outer ends while each free a to slsts oi. one jot the'opposed engi. clprocatlng m cylinder/ta comp reciprocating in each or, the cylino buffer piston reciprocating in. each of the inders 3. In the .headof each'comr eesei iriderfl is at least one inlet valve 5 put the cylinder in com annica as which can putthe' cy'lizi port la in. the engine cylinder 5.; =.e

nular spacefeommunicaiting with the Y {list conduit it;

The reciprocating piston unitsare synehrer sec: in well known and usualinanner by beingllnir by -thepair oflink l to the opposite en the lever 8- having its mid point pivoted;-

tn be injected into the cylinder I by fuel ll of conventional form supplied through is ill, the usual form of distributor i8 "is fuel pipes l9 by the fuel injection pump oi conventional form reciprocated by cam H h i oscillated (in accordance with the moveof the free piston units) by the bell-crank lever 23 which is connected by link 2| to a point on. one of the links I. The quantity of fuel in- .iected by each stroke of the injection pump I is determined in the usual manner by the posioi the fuel rack Illa. ach bufier cylinder 3 is provided with an ping controlled by the non-return valve 22 rniing an inlet valve through which compressed us. In addition, each buffer cylinder has a governed by the compression relief valve 21 can be opened by the application of fluid insole from pipe 26. barring piston 24 movable in cylinder 25 is "ovided for moving the opposed piston units and out to the extreme outer end of their he on the stopping of the engine; the pistons c left in this position ready for restarting. This tting operation is performed in response to re application of fluid pressureto the cylinder ough resetting control pipe 26 which, while ngine is running, is disconnected from the nor as hereinafter described. The'reset- '3 controlled by a barring relay"-comprisa valve device made up of pistons 30v and 3| his in cylinder body 32 by the application of pressure thereto from pipe 33--in co-operal with an end of stroke indicator comprising a triple piston valve 34 movable in cylinder also in part by the application of fluid presthereto from pipe 33 and partly by the attainthrough link 29-of the opposed engine dead centre position.

in one extreme position this valve 35. conone of two longitudinal" cylinders in the igh a comparatively'restricted oriflce 3117' the other of said cylindersto exhaust a similar orifice 31a; in the other excsiticn the valve 36' reverses these conwhile during its movement from one :1 to the other the valve temporarily conbe h cylinders to exhaust. In each cylinder e of a pair of double pistons, 33 and which, s fluid pressure through orifices 31a and 31b, cove outwards against a very light biassing serve together to connect the pipe rhaust through port 31c only when applied inby the blessing force of spring 14!, the is connected to the fluid pressure pipe 42.

iv be in a position in which at least one of said cylinders of the runningin'dicator is connected-to exhaustiand so the pipe 33"will be heated to pressure. When the engine is runand the control valve 36 is being reciprocan be admitted from pipe 23 for starting the is whenthey reach or closely approach their ining indicator" (Fig. 4a) isfa hydrau omprising piston valve 36 reciprocated link 23 in a transverse cylinder in the body body to fluid pressure supply .pipe 38' 36 provided by springs 4|. These pistons form c has moved both pistons. out; wheneither V the engine is at rest the control valve3G' cated by the link 28 the said cylinders are connected alternately to pressure and to exhaust but they are not connected to the exhaust long enough through the restricted orifices 31a and 31b for the light biassing force of springs 4| to impart any appreciable inward movement to either piston; accordingly both pistons remain out and the pipe 33 remains connected to exhaust,

The fluid pressure in pipe 33--as soon as the engine stopsmoves the piston unit 34 01' the end of stroke indicator outward to a position in which it can be operated by motion of the free pistons and by acting on the smaller piston 30 of the barring relay moves this also in 0ne direction, to allow the fluid under pressure to pass by way of pipe 26 to open the compression relief valves 21 in the buffer cylinders and also to enter the barring cylinder 25, thus causing the barring piston 24 to move outwards and drive the free pistons to their outer dead centre position. When the free pistons approach or reach their outer dead centre position a cam 43 actuated by them through link 29 and the lever 20 connected by the link 2| to the synchronising linkage, is rocked about the fixed pivot 44 toengage a roller 45 on the projecting end of the piston rod of the end of stroke indicator, forcing the triple piston 34 inwards to the position shown in Figures 4 and 5 and therebygconnecting the fluid pressure from pipe 33 by way of pipe 46 to a rear part of the barring relay, behind the piston 3| which is shown as of greater area than the front piston 30 so that, the force from the rear will overcome that from the front. The latter relay is thus moved back to its normal position (as shown) to disconnect pipe 26 and the barring cylinder 25 from the pipe 33 and to connect them to the exhaust E, whereby the barring piston 24 is withdrawn by the action of a blessing force such as that of a spring 41 and the relief valves 21 in the buffer cylinders 3 can reclose. The barring piston 24, when completely withdrawn, re-establishes a connection from the pipe 33 through the "end of stroke indicator cylinder 35, pipe 46, and ports uncovered and put into communication by the re-' duced portion 24a of the piston rod of the barring piston ,24-:-'t'o pipe 48 and a port in a starting relay'."-49 hereinafter described with reference to place automaticallyin immediate response to the stopping of the engine.; 1 V i.

Referring. now also to Fig. 3,ithe engine of each componentcan be started by the application of fluid pressure throughpipe 15 to the cylinder of the starting relay 49;'the resulting movement of the piston valve 50 therein againstthe force of through pipe 54 with the cylinder 55 of the servomotor for actuating thestarting valve; Movable within cylinder 55 is a pistonunit' made. up of parts 56 and 51 with spring 58 compressedbetween them; the part 51 can engage the Stem of starting valve 59 which, "when the valve is closed, rests on a seating in the valve casing 60. Provided that the corresponding running, indicator is in the rest position, that the end of 7 stroke indicator? is in the. position corresponding to the free pistons being in the outer dead centre position and that the barring piston is fully withdrawmit will be clear that fluid under pressure can then 'passfrom the supply pipe 42 through the pipes 33, 46,. B8 and 54 to the cylinder55 and so cause piston part 51 to lift the starting valve 59 off its seating. Compressed air for starting purposes from pressure pipe 6lwhich constitutes a source of comparatively unrestricted capacity-is hence admitted to the now closed buffer piston device. Subsequent reclosure of the cylinders '3, by way of pipe 62, the body 630i 9. v

"timing valve" provided for subsequently cutting ed the air supply to the cylinders 3, the pipe 23.

Thetiming valve-64 has three positions in the body 63, viz: (1) closed, (2) fully open, and (3) wholly released; it is biassed to position (3)- in which it is shown in Figure 4--by a spring 65 which, holds the valve considerably clear of its seating. ;The valve device includes a lever 66 pivotally'mounted outside the valve casing on 9. lug 61 extending therefrom; atrigger 68 is pivotally mountedon this lever and normally positioned directly adjacent to the end of the stem 64a of valve 64, which stem projects through the valve casing 63. The lever 66 is biassed by gravity to a position in which the trigger 68 abuts against thevalve stem 64a but the lever is free to make a small movement until arrested by a stop formed by the lug 61. The pressure of the air'entering body 63 from pipe 62 acts on the .timing valve 64 itselfto move'it (against the biassing force of spring 65) from position (3) to its-position (2) or "fully open position (Figure '5) thus allowing air to pass by pipe'23 to thebuffer' cylinders 3. Preferably in position (3) a collar 64b on' the valve stem 64a lying within" and considerably scribed below. The valve stem 64a, during the:

movement of the valve to the open position, bears against the trigger 68. which with lever 66 thus acts as a stop. The thrust of the valve stem against the trigger is on a line-passing through the pivot of the trigger which therefore does not 'operationof the engine, and from pipes and 54 so that the pistons 56 and 5? will allow timing valve mechanism does not n with subsequent normal operation. of

ter starting valve 59 (cutting oil the su;

'air) allows the, timing valve to return up the action of its biassing spring 55 and tog with the lever 66 and trigger 68 to the w disengaged position so that the trigger out of the path of the member adapted to engo.

it. The-movement of the free pistons will actuate the running indicatorfto disconnect the pipe 33 from the supply pipe t2 and connect it to exhaust. Pressure is thus removed from the piston unit 34 of the end of stroke indicator,

which will accordingly remain in the withdrawn position and be unaffected by the subsequ the .master starting valve 53 to reclose.

turn about its pivot but the lever 66 moves-until arrested by the stop. This movement of the valve and trigger, by which the valve moves to but is held in the fully open position, brings a part of the trigger 68 'into the path of a part of the cam 43 actuated by the free pistonsthrough link 29. As the pistons pass a certain point before reach- I ing the inner dead centre position, the trigger $8 is accordingly'engaged by-cam 43 and turned The valve stem 64a then bears onthe'trigger (i8 in such a way as to hold it out of the path of the cam 43 as the latter oscillates. that the starting air supply is cut off and the Itwill be seen' The engine of each component is stopped or cutting off the fuel supply-i. e. by moving fuel rack iila which controls the fuel supply e power output to the position in which the fuel pump l0 delivers no fuel. .This fuel pump, as indicated in Fig. l by the chain-dotted line extending from the fuel-rack iila, is mechanically linked to and hence actuated by one of the fluid pressure servo-motors Lilli), Milli], etc. which is also mechanically connected to and acted 0 one of the counter-pressure devices Liel, etc. Also associated with the servo-mot throw-over valve device such as List,

7 Similar partsassociated with eachof the ponents are indicated in Fig. l by the same ence numerals but with the distinguis fixes L, M, N or P, these prefixes in Figs. 3 and 4] The exhaust pipesLIG, MIG, etc. all dischainto the common supply conduit it? going to inlet to the turbine 13 shown in Fig. 2. speed governor I0 3 of the turbine actuates i usual valve device I05 to connect the control pi e l06'to fluid pressure on a decrease in speed below and to exhaust on an increase in speed above predetermined value.

Fig. 3'shows the fuel pump it for any of the components, also in longitudinal sect on servo-motor device we actuating the r the counter-pressure device till o servo-motor and the associated throv eve device Illl. The servo-motor compriees der I08in which a piston Hi9 operating t rack ma is moved forward by fluid under from the control pipe it through over valve. Backward movement of the n 19 is limited by a releasable stop il'fi oc with a stop piston Ill (of larger eifect than the piston 10!!) movable in an eaten the cylinder I08. The stop piston i i in its right-hand position by fluid pr'essu mitted through pipe. H3; this may act as through a further piston M2 for a purpose plained hereinafter. Movement of piston increase the quantity'of fuel injected is 'o co bybiassing spring ilfi and can be oppos bya counter-pressure piston 'i it movais cylinder H? of the device iii'l by fiuid'ul. e sure through the pipe33- from the asst running-indicator when the associated component is at rest. a

The throw-over device iDl consistsof I I8 movable from one end to the other of cyt: H9 under fluid pressure from one or other of pipes 26. As already explained; pressure is plied through pipe 26 momentarily, and in sponse to the stopping of the component, to the barring device for resetting the pistons. Pipe L26 from component L goes to the right-hand end of device LIOI and to the left-hand end of device MIOI, the pipes M26, etc., being similarly connected (see Fig. 1). Thus the valve I I8 has pressure applied to it for a brief period immediately after its associated engine is stopped, tending to move it to the left, to a closed position; an equal and opposite pressure tending to move it to the right-4. e. to the open position in which it connects the control pipe I06 through pipe III to port I08ain cylinder I08 is applied for a brief period immediately after the preceding engine in cyclic order is stopped. When no pressure is applied thereto, the valve .I I8 stays in whichever position it has been previously set, and may be lightly retained in position by spring-pressed ball catch I20. Thus the first component to start will have its throw-over valve device MI in the open position and the others should'have their throw over valve devices IOI in the closed position. The valves II8 will have automatically been left in suitable positions as a result of the functioning of the plant during its preceding period of operation and by the stopping of the last engine at the end of that period. Alternatively the throwover valves II8 may be set manually by the projecting piston rods I22 with any desired engine arranged as the first to start. The initial start is obtained'by moving the rod 50a of the device 49 to the right by hand as described. Starting of subsequent engines in cyclic order has no effect on the throw-over valve devices IOI but stopping of the first engine causes its throw-over valve H8 to be moved to the closed position while that associated with the next engine is moved to the open position.

When for example only the one component L 'is running; the control pipe I08 is connected through device LIOI 'directly to the associated servo-motor LI00. n a momentary decrease in rbine speedthe turbine governor valve I05 connects fluid pressure to the control pipe I06 whereby the piston I 09 of servo-motor LI00 is moved to the right to increase the output of engine LI. This continues progressively untilthis particular piston I09 uncovers a port I08d in the cylinder .508, putting the'control' pipe I06 (through pipe I2I) in communication with the pipe M75 going to the starting relay M49 for Movement of this relay connects fluid pressure from pipe M48 to the servo-motor which opens master starting valv M55 to start the engine MI; The movement of any starting relay 49 (such as M49) also allows the pressure fluid to pass through it by wayof pipe I23 and non-return valve I24 to the port I08b in the associated servomotor cylinder and act on the piston I09-e. g. for M. Since the throw-over valve device MIDI is in the closed position, there will be no connec-' tion from the control pipe through this valve to the servo-motor cylinder for M but control pipe I06 is in communication, through pipe I I3,'w'ith the cylinder extension so that pressure holds the stop piston III and the stop H0 in their forward position whereby the servo-motor piston I09 for M is held in a position to adjust the fuel pump to supply a certain smallquantity of fuel toengine .MI, which should accordingly immediately start. It is possible that through leakage in the system while the engine is at rest there may be the component M.

p in an immediat adjustment of their combined 7 return valve I26 come this difllculty the cylinder II! of the associated counter-pressure device I01 receives fluid pressure through pipe .33 from the associated running indicator while the engine is at rest. which pressure acts on the counter piston to 0ppose movement of the piston I09 and of the rack I0a beyond a predetermined position corresponding to the maximum quantity of fuel it is desired to supply when starting.

The starting of engine MI will cause pressure to be removed from the counter pressure device MI01 and there may accordingly be an immediate tendency for the associated piston I09 to move and increase the fuel supply to the engine MI. The starting of the latter will, however, probably immediately result in the combined output of the two components L and M being more than sufficient to meet the load requirements of the turbine I03 which will accordingly increase in speed sufliciently for the turbine governor to connect the control pipe to exhaust. The servo-motor piston I09 of device LI00 can clearly then move backwards under the action of the associated biassing spring I I5 to reduce the output of engine LI; thus the starting of the engine MI will result in a reductionof the'output of component L and output to meet the load requirements of the turbine I03. If the piston I09 of device MI 00 has moved forward beyond the initial starting output position it will be able at once to move backward-as described belowm reduce the output of component M again} and ensure the necessary adjustment of the combined output.

When the piston I09 of device LI00 has moved back far enough to cover again the port I08d fluid from the cylinder I08 of device MI00 cannot return to exhaust by this route, nor can it return by the throw-over valve device MIOI. Another pipe I25 is provided, however, by which fluid can flow from port I08b in each cylinder I08 to the control pipe I06 through a second nonpreventing flow in the reverse direction. Thus when the pressure in the control pipe I06 falls below the pressure of fluid trapped behind the piston I09 of device MI00 the associated non-return valve I26 can open to permit fluid to flow out of device MI00 to permit the associated biassingspringIIS to move the rack I0a of the fuel pump MIO to reduce the output of engine MI.

Further increase in load will move the piston device for the whole plantthe piston I09 for an accumulation of fluid in the cylinder I08 which.

might tend to adjust the fuel more fuel than desirable for pumpIO to supply starting; to overengine M I will move forward only so long as the said port I08d of the device LI00 is uncovered. With further increase of load the piston I09 of device MI 00 will uncover its associated port I08d to bring the engine NI into action as already described but thedevice Ll 00 will still remain the master device controlling devices M I00 and N I00 and device I00 of any component subsequently started.

On progressive decrease of load the pistons I09 of devices LI00, MI00, etc., for all the engines in operation can move backward (to the left) until each engages its stop IIO but further this device LI will be opposed by the pressure from the control pipe I06 acting on only the piston I 09 whereas the counter-springs II of the devices ME 00, etc., will be opposed by the pressure from the control pipe I06 acting on the larger stop pistons IN or H2. If the pistons I00 of all the devices I00 are engaging their stops H0 and stop pistons then when next the governor valve I05 connects the control pipe I06 to exhaust, the counter-spring II5 acting on piston I09 of device LI00 can move that piston (together with the associated stop H0 and stop piston III) backward to move the rack I0a of pump LIO to decrease still further the fuel supply to engine LI and eventually to cut off the fuel supply and so stop engine LI. This is possible because the throw-over valve device LIIlI is in the open position and has cut off pipe I I3 connecting the back of the associated stop piston from the pressure in the control pipe I06 and connected this pipe H3 either to exhaust or to some independent source of lower pressure. In the arrangement shown the pipe I I3 from device LI00 is connected to pipe P26 to which there is no pressure except momentarily on the stopping of engine PI. The pistons I09 of devices I00 for the engines subsequently brought into operation, when engine L8 is being stopped, position the corresponding racks I00, in the minimum fuel position, but they will begprevented from so great a further backward movement icy their stops IIildue to fluid pressure through the pipes I I3 acting on the back of each stop piston and so only the engine Ll will stop.

The stopping of engine LI applies fluid pressure momentarily through pipe L26 to the cylinder N0 of device LIDI to move valve IIS thereof to the closed position whereby pressure from pipe 230 is f e-applied through pipe M3 to the back of associated stop piston to move the piston I00 of device LI 00 forward to a minimum fuel position \inreadiness, for the restarting of engine LI.

Pressure is also applied through pipe L26 to the cylinder I I9 of device MIOI to move valve N3 of device M501 to the open position; this connects the control pipe I08 through pipe Hi to device MI00 whereby the latter becomes the master servo-motor? device for the whole plant.

The associated, non-return valve I20 is closed by the back pressure of the fluid in the cylinder Hi8 of device MI00, which pressure accordingly cannot affect the associated starting relay M 59 or pass back through pipe L15 to the port 50802 in the cylinder I08 of the device U00. To guard against any risk of slight leakage past the nonreturn valve I20 the starting relay 59 may be arranged so that in the idle position, as shown in Fig. 3, the pipe I23 is connected to drain. This same non-return valve I24 can fulfill another important function, as described below.

A further feature of the invention allOWs the starting signal, from each component to the next, to be transmitted when the output of the component is still some fraction below its maximum while at the same time ensuring that, if more than one component is in operation, all components other than the last to start will reach full output before a starting signal is transmitted to any further components. To achieve this result each of the non-return valves I24 is loaded, so as to act as a reducing valve whereby when the controlling fluid is flowing from the device M0 for one component 'through the associated valve I2 3 to that for the next component and so move the associated rack Illa into the full output position before the piston I09 of the next device MI00 uncovers the port I08d in its cylinder.

Thus it will be seen that the arrangement controls the output of the whole plant in accordance with the load on the turbine I05 and ensures both starting and stopping of individual components in the same cyclic order. During the operation,the fuel pumps I0 for the various engines will not necessarily be all similarly adjusted but at certain times willas an inherent feature of the operation of the arrangementbe adjusted to different outputs. The engines will thus not necessarily operate all at the same outputassuming that they are identical and consequent-- 1y have the same maximum output. The arrangement may be such that under most conditions all the engines except one are working under approximately optimum conditions. An additional feature of the invention assisting towards the maintenance of as many engines as possible at or near their full load consists of the provision of a small leak from each servo-motor cylinder. With the plant running under steady load conditions this leak will result in a tendency for the output of all the components in action to fall slowly. This fall in output will be corrected by the governor valve I05 admitting more pres sure fluid to the control pipe I06 but this additional fluid will act on the devices I00 and hence on the engines in cyclic order so that under the final steady conditions that one of the components in action which is last in cyclic order may be operating on part load whilst all other components in operation are operating at full load. Alternatively the last component in cyclic order may be at minimum load (i. e. with the servo-motor piston against the stop), the next engine to it may be operating on some greater fraction of full load whilst all other engines in operation are operating at or near full load.

According to a further feature of the invention, reduction of load is efiective to stopan engine only if the next engine in cyclic order is running; this ensures that when only one engine is running this engine can be stopped, and the plant completely shut down, only by the action of an attendant. To this end pressure is also applied to each stop piston device while the next engine in cyclic order is at rest-which pressure can conveniently come from the signal pipe 33 controlled by the running indicator of the next engine. Thus, as shown, the stop piston is in two separate parts III and H2, the former having a projection bearing against the back of the stop IIO and the rear part H2 having a projection bearing against the back of the part III; a port I000 in the cylinder extension between these parts .I I I and H2 is connected to one of the signal pipes 33 while the back of the cylinder extension can be connected--as already describedto the associated throw-over device I0 I. The device LI00 is connected to pipe M33, device MI00 to N 33 and so on. The stop I I0 itself is shown as an independent piston located in the cylinder I08 between the forward projection from part III of the stop piston device and a rearward projection from the piston I09. A leak is shown at the front end of the cylinder extension for draining 11 off any fluid leaking from the servo-motor cylinder.

The number of components of the plant may I be more than is necessary to deal with the maximum load on the plant so that there will always be at least one engine at rest serving as a standby and this will allow at least one engine to be shut down for inspection and repair at any time, while leaving the plant capable of dealing if necessary with the maximum load.

What I claim as my invention and desire to secure by Letters Patent is:

-1. Power plant of the kind including a prime mover, a speed governor actuated thereby, a governor-valve device actuated by said governor, and a plurality of internal-combustion compressors supplying motive gas in common to said prime mover, in combination with fluid-Pressure type means for controlling the output of said in ternal-combustion-compressors and for starting and stopping them successively in the same cyclic order, which means comprise, for eachof said internal combustion compressors, (i) a starting device, (ii) a fuel-supply regulator-having a "stop" (1. e. no-fuel) positionav maximum fuel position and a range of intermediate positions, (iii) a fluid-pressure type servo-motor in driving connection with said fuel regulator, (iv) supply pipes from said governor-actuated valve to said servo-motor, (v) a pipe connection to the starting device for the next internal-combustioncompressor in the said cyclic order from a port in said servo-motor positioned to be uncovered when servo-motor and fuel regulator are in an intermediate position, (vi) a movable stop of said servo-motor retained by fluid pressure in position to obstruct movement of said servo-motor and fuel-regulator to the "no-fuel" position, and (vii) a throwover control valve in the fluid pressure connection to said movable stop.

2. Power plant according to claim 1 including a non-return valve in the pipe between said port in the servo-motor and the said starting device of the next compressor in cyclic order.,

3. Power plant according to claim l'including, for each said internal-combustion-compressor a running-indicator actuated thereby and operative connections between said throw-over valve and firstly the rimning-indicator for the associated internal-combustion compressor and secondly the running-indicator for the preceding compressor in cyclic order, the connections being in such a sense that the throw-over valve device is movable in response to the stopping of the preceding compressor in cyclic order to take up a position in which it connects the associated servo-motor device to a fluid pressure supply pipe controlled by said governor actuated valve and to take up a position interrupting that connection in response to the stopping of the associated compressor whereby the said connection to the supply pipe controlled by the governor actuated valve is established only for that one of the compressors in action which is first in cyclic order.

4. Power plant according to claim 1 including for each said compressor a running-indicator actuated thereby, a further arresting member in co-operation with the said arrestin ember, and a fluid-pressure connection established to the latter by the said running indicator of the next internal-combustion-compressor in the said cyclic order when this next compressor is at rest and accordingly theassociated internal-combustion-compressor is the only one running.

5. Power plant of the kind including a prime mover, a speed governor actuated thereby and a plurality of internal combustion compressors supplying motive gas in common to said prime mover including, for each'of the said internal-combustion-compressors (i) a combination of a fuelsupply regulator-having a stop (1. e. no fuel) position-with an actuating servo-motor therefor'under the control of said governor, (ii) a pressure-reducing valve controlling the supply to said servo-motor independently of those associated with the other internal-combustion-compressors, (iii) a movable stop on said servo-motor retained by fluid pressure in position to obstruct movement of said servo-motor and fuel regulator to the no-fuel position and (iv) a throw-over valve in the fluid pressure connection to said movable stop.

ROBERT JAMES WELSH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,237,082 Pateras-Pescara Apr. 1, 1941 2,306,978 Pateras-Pescara Dec. 29, 1942 FOREIGN PATENTS Number Country Date 439,666 Great Britain Dec. 11, 1935 183,759 Switzerland July 16, 1936 

